title: Purification of contaminated paddy fields by clean water irrigation over two decades.
abstract: Paddy fields near a mining site in north part of Guangdong Province, PR China, were severely contaminated by heavy metals as a result of wastewater irrigation from the tailing pond. The following clean water irrigation for 2 decades produced marked rinsing effect, especially on Pb and Zn. Paddy fields continuously irrigated with wastewater ever since mining started (50 years) had 1,050.0 mg kg−1 of Pb and 810.3 mg kg−1 of Zn for upper 20 cm soil, in comparison with 215.9 mg kg−1 of Pb and 525.4 mg kg−1 of Zn, respectively, with clean water irrigation for 20 years. Rinsing effect mainly occurred to a depth of upper 40 cm, of which the soil contained highest metals. Copper and Cd in the farmlands were also reduced due to clean water irrigation. Higher availability of Pb might partly account for more Pb transferred from the tailing pond to the farmland and also more Pb removal from the farmland as a result of clean water irrigation. Neither rice in the paddy field nor dense weeds in the uncultivated field largely took up the metals. However, they might contribute to activate metals differently, leading to a different purification extent. Rotation of rice and weed reduced metal retention in the farmland soil, in comparison with sole rice growth. Harvesting of rice grain (and partially rice stalk) only contributed small fraction of total amount of removed metal. In summary, heavy metal in paddy field resulting from irrigation of mining wastewater could be largely removed by clean water irrigation for sufficient time.
authors.affiliation: Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Xingke Road 723, Tianhe District, Guangzhou, People’s Republic of China.
authors.forename: Yiping
authors.initials: Y
authors.lastname: Tai
authors.forename: Huanping
authors.initials: H
authors.lastname: Lu
authors.forename: Zhian
authors.initials: Z
authors.lastname: Li
authors.forename: Ping
authors.initials: P
authors.lastname: Zhuang
authors.forename: Bi
authors.initials: B
authors.lastname: Zou
authors.forename: Hanping
authors.initials: H
authors.lastname: Xia
authors.forename: Faming
authors.initials: F
authors.lastname: Wang
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Duan
authors.forename: Jianxia
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000383:Agriculture; D002681:China; D004784:Environmental Monitoring; D004787:Environmental Pollution / Q000517:prevention & control*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry*; D008906:Mining; D012275:Oryza / Q000254:growth & development; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D013054:Spectrophotometry, Atomic
chemical_list: D019216:Metals, Heavy; D012989:Soil Pollutants